Various clinical and scientific disciplines monitor the electrical activity of tissues in living organisms, for example, monitoring signals arising from the heart via electrocardiography (ECG), the brain via electroencephalography (EEG), skeletal muscle via electromyography (EMG), and the like.
Common to acquisition of typical major electrophysiologic data are signal conditioning stages consisting of pre-amplification (mono-, bi- or multi-polar), high-pass filters (to reject motion artifact), low-pass filters (to reject noise out of band and for anti-aliasing), gain selection and digital to analog conversion. For multiple channels, multiplexing must also occur.
Typically, distinct instrumentation is designed for each electrophysiologic signal, and for different applications related to each signal—for ambulatory recording (e.g., telemonitoring), low-power design is emphasized; for multiple-channel systems, cost, size and complexity are minimized, and the like. In most cases, systems comprised of numerous discrete analog and digital electronic components per electrophysiologic channel are employed. Cost (often $500-1000/channel), size, complexity, power consumption and availability have slowed the proliferation of multiple channel systems in certain areas of medical research. For example, in ambulatory systems, power consumption can be a limiting factor.